1. (a) Field of the Invention
The present invention relates to ladder polysilanes which are novel compounds, and a method for preparing the same.
2. (b) Description of the Prior Art
In recent years, the technology of organic silicon chemistry has advanced actively and rapidly, and a variety of cyclopolysilanes having high strain become now already synthesized. For example, there are [(CH.sub.3).sub.2 Si].sub.6 in J. Am. Chem. Soc. 71, 963 (1949); [t-Bu(CH.sub.3)Si].sub.4 (Bu is a butyl group) in J. Organomet. Chem., 77, C13 (1974); (Mes.sub.2 Si).sub.2 (Mes is a mesityl group) in Science, 214, 1343 (1981); (Ar.sub.2 Si).sub.3 (Ar is a 2,6-dimethylphenyl group) in J. Am. Chem. Soc., 104, 1152 (1982); [t-BuCH.sub.2).sub.2 Si].sub.3 and [t-BuCH.sub.2).sub.2 Si].sub.2 in Chem. Commun. 781 (1983); and (t-Bu.sub.2 Si).sub.3 and (t-Bu.sub.2 Si).sub.2 in Organometallics 1983, 2, 1464, and Journal of Organometallic Chemistry, 282 (1985) 305. In addition, examples of the cyclopolysilanes having silyl groups on side chains thereof include [[(CH.sub. 3).sub.3 Si].sub.2 Si].sub.4 in Organometallics, 1410 (1982), [[(C.sub.2 H.sub.5).sub.3 Si].sub.2 Si].sub.3 in Japanese patent application No. 61-210718, and [[(C.sub.2 H.sub.5)(CH.sub.3).sub.2 Si].sub.2 Si].sub.4 in Japanese patent application No. 61-210719.
These high-strain cyclopolysilanes have great strain energy and are thermally reactive, and therefore they are used as reagents for reactions with various molecules. The Si--Si bond in the cyclopolysilane is easily decomposed by light irradiation (about 200 to 400 nm) to release silylene (.dbd.SiR.sub.2), and thus by the utilization of this, various photoreactions can be carried out. In particular, the cyclopolysilane having the silyl groups on the side chains thereof contains many Si--Si bonds, and therefore it can be presumed that the photoreactivity of the cyclopolysilane is extremely high. Furthermore, the cyclopolysilanes which have undergone ring opening polymerization can be utilized in a wide range as raw materials for polymers and SiC ceramics and as photoresists, and for this reason, the cyclopolysilanes are expected.
Moreover, chain polysilanes represented by the formula ##STR2## wherein x and y are each a positive integer, and R' is an alkyl group, a phenyl group or the like, having easy workability has been discovered of late [J. Am. Ceramic Soc., 61, 504 (1978)]. Since the chain polysilanes have electric conductivity and photosensitivity, development has been actively made to utilize them as functional materials such as photoresists, semiconductors and prepolymers for ceramics.